The present invention concerns isolated DNA encoding chemoreceptors of plant parasitic nematodes, cells that express such DNA, the proteins so expressed, and methods of use thereof.
Annual crop losses to plant-parasitic nematodes (soil-dwelling microscopic worms) are estimated to exceed 70 billion dollars world-wide. The soybean cyst nematode (SCN), Heterodera glycines, causes about one billion in annual soybean losses in the United States alone. Environmental restrictions in the use of toxic nematicides and limitations in available plant resistance schemes to nematodes have prompted an urgent need for alternative management strategies to reduce nematode-related damage in agriculture.
One way to control nematodes is by understanding and specifically interfering with the nematode""s ability to locate and feed from plant roots. Like most plant-parasitic nematodes, infective juveniles of SCN migrate in the soil and use their neurosensory organs to follow chemical signals emanating from host roots that they will attack
Chemoreceptor molecules have been identified in the model nematode, Caenorhabditis elegans, as described in S. Yu et al., Proc. Natl. Acad. Sci. USA 94, 3384-3387 (1997). However, essentially nothing is known about putative chemoreceptors in plant-parasitic nematodes. Accordingly, there is a continued need for more information about the chemoreceptors of plant-parasitic nematodes.
A first aspect of the present invention is an isolated DNA encoding a nematode guanylyl cyclase chemoreceptor selected from the group consisting of: (a) isolated DNA having a nucleotide sequence selected from the group consisting of SEQ ID NO: 1, SEQ ID NO: 3, SEQ ID NO: 4, and SEQ ID NO: 6; (b) isolated DNA that hybridizes to DNA of (a) above under stringent conditions and encodes a nematode guanylyl cyclase chemoreceptor; and (c) isolated DNA that differs from the DNA of (a) or (b) above due to the degeneracy of the genetic code, and encodes a nematode guanylyl cyclase chemoreceptor encoded by (a) or (b) above.
In one particular embodiment of the invention, the isolated DNA is selected from the group consisting of: (a) isolated DNA having a nucleotide sequence selected from the group consisting of SEQ ID NO: 4 and SEQ ID NO: 6; (b) isolated DNA that hybridizes to DNA of (a) above under stringent conditions in which said isolated DNA does not hybridize to DNA having a nucleotide sequence of SEQ ID NO: 1, and encodes a nematode guanylyl cyclase chemoreceptor; and (c) isolated DNA that differs from the DNA of (a) or (b) above due to the degeneracy of the genetic code, and encodes a nematode guanylyl cyclase chemoreceptor encoded by (a) or (b) above.
In another particular embodiment of the invention, the isolated DNA is selected from the group consisting of: (a) isolated DNA having a nucleotide sequence selected from the group consisting of SEQ ID NO: 1 and SEQ ID NO: 3; (b) isolated DNA that hybridizes to DNA of (a) above under stringent conditions and encodes a nematode guanylyl cyclase chemoreceptor; and (c) isolated DNA that differs from the DNA of (a) or (b) above due to the degeneracy of the genetic code, and encodes a nematode guanylyl cyclase chemoreceptor encoded by (a) or (b) above.
In another particular embodiment of the invention, the isolated DNA is selected from the group consisting of: (a) isolated DNA having a nucleotide sequence selected from the group consisting of SEQ ID NO: 4; (b) isolated DNA that hybridizes to DNA of (a) above under stringent conditions and encodes a nematode guanylyl cyclase chemoreceptor; and (c) isolated DNA that differs from the DNA of (a) or (b) above due to the degeneracy of the genetic code, and encodes a nematode guanylyl cyclase chemoreceptor encoded by (a) or (b) above.
In still another particular embodiment of the invention, the isolated DNA is selected from the group consisting of: (a) isolated DNA having a nucleotide sequence selected from the group consisting of SEQ ID NO: 6; (b) isolated DNA that hybridizes to DNA of (a) above under stringent conditions and encodes a nematode guanylyl cyclase chemoreceptor; and (c) isolated DNA that differs from the DNA of (a) or (b) above due to the degeneracy of the genetic code, and encodes a nematode guanylyl cyclase chemoreceptor encoded by (a) or (b) above.
Preferably, the encoded nematode guanylyl cyclase chemoreceptor is selected from the group consisting of order Tylenchida and order Aphelenchida chemoreceptors.
A second aspect of the invention is an oligonucleotide that specifically binds to isolated DNA as described above is a further aspect of the invention. Such an oligonucleotide may comprise DNA or RNA, or may be a synthetic oligonucleotide.
A third aspect of the invention is an antisense oligonucleotide that specifically binds to an mRNA transcript of a DNA as described above, along with DNAs that encode such antisense oligonucleotides.
A fourth aspect of the invention double-stranded RNA that is complementary to a DNA as described above and interferes with the expression thereof in a cell that expresses the encoded protein.
A fifth aspect of the invention is an expression cassette comprising a DNA as described above and a heterologous promoter operatively associated therewith, along with cells that contain such expression cassettes and express the encoded nematode guanylyl cyclase chemoreceptor (e.g., yeast cells, plant cells, insect cells).
A sixth aspect of the invention is an isolated nematode guanylyl cyclase chemoreceptor protein encoded by a DNA as described above (a protein of the invention), along with proteins or peptides (e.g., antibodies) that specifically bind to such nematode guanylyl cyclase chemoreceptor proteins.
A seventh aspect of the present invention is a method of screening a compound for the ability to disrupt plant parasitic nematode feeding or chemotaxis, said method comprising: determining whether or not said compound selectively binds to a nematode guanylyl cyclase chemoreceptor protein encoded by a DNA as described above. The presence of such binding indicating said compound is useful in disrupting plant parasitic nematode feeding or chemotaxis.
The foregoing and other objects and aspects of the present invention are explained in detail in the specification set forth below.